/Engine/Source/Runtime/UMG/Public/Blueprint/WidgetBlueprintLibrary.h
Ask Slate to detect if a user starts dragging in this widget later. Slate internally tracks the movement and if it surpasses the drag threshold, Slate will send an OnDragDetected event to the widget.
static [FEventReply](API\Runtime\UMG\Components\FEventReply) DetectDrag ( [FEventReply](API\Runtime\UMG\Components\FEventReply) & Reply, [UWidget](API\Runtime\UMG\Components\UWidget) * WidgetDetectingDrag, [FKey](API\Runtime\InputCore\FKey) DragKey )